As requisite feature, or critical dimension (“CD”), sizes continue to decrease in microelectronic devices, masking continues to be a challenge. Research and development into patterning cameras and materials integrations consume significant resource to this end, with some cameras costing in the range of $20 million, and some resist materials costing in the range of $5,000 per quart.
Referring to FIGS. 1A-1F, a conventional patterning treatment is depicted. As shown in FIG. 1A, a mask layer (102) is positioned adjacent a substrate layer (100). Upon the mask layer (102), a resist layer (104) is formed to facilitate subsequent patterning of the mask layer (102). Referring to FIG. 1B, patterned irradiation (106) from a conventional camera is utilized to expose portions of the resist for selective removal and creation of trenches (110, 112, 114), as depicted in FIG. 1C. With a conventional resist material, the trenches (110, 112, 114) are formed using a solvent. The patterned resist layer (108) may then be utilized to guide the formation of trenches into the mask layer (102), as depicted in FIG. 1D. With a conventional mask layer (102) material such as chromium, a chlorine-based etch chemistry may be utilized to facilitate removal of desired chromium material. Such etch chemistries typically also are effective at removing resist material, and therefore a thinned patterned resist layer (116) results from such exposure. To prevent small defects or pinholes in the thinned patterned resist layer (116), the unmodified resist layer as depicted in FIG. 1A (104) typically is formed with extra thickness. For example, in a scenario where about 1,000 angstroms of chromium mask layer (102) are to be etched through, a resist layer having a thickness between about 3,000 and 4,000 angstroms may be sufficient at the outset to result in a final thinned patterned resist layer (130) thickness, as depicted in FIG. 1E, of about 1,500 angstroms—which may be thick enough to avoid unwanted defects and pinholes. Referring to FIG. 1F, the final thinned patterned resist layer (130) is subsequently removed to result in a final patterned mask layer (132).
It is known that the irradiation exposure intensity decays exponentially with depth into a targeted resist layer, such as that depicted in FIG. 1B under irradiation, and that this exponential decay in exposure intensity causes mask layer (102) CD to be approximately proportional to resist layer (104) thickness. Efforts to decrease CD, therefore, have resulted in significant work to develop resist materials, such as those mentioned above, which provide the requisite patterning functionality without pinholes or other inadequacies, such as uniformity degradation. The chemistry issues to this end are significant, and there is a need for other solutions to facilitate low-CD patterning.